Bird composition of oak ecosystem fragments in an urbanized setting: The influence of adjacent coniferous forest fragments

Bird composition of habitat fragments in urban areas is expected to he associated with adjacent landscape and with smaller-scale factors within fragments. This study investigated the bird assemblage of coastal oak (Quercus garryana) fragments in British Columbia, Canada adjacent to either coniferous forest or urban development. Effect of habitat type (oak, conifer, urban) and local habitat differences (tree volume, shrub cover, grass cover) on the composition of the bird assemblage was also determined. During the 2000 breeding season, birds were surveyed in a 50-m fixed-radius point count at stations along two transects within each habitat type. Bird assemblages were most different between forest and urban habitat. The bird composition of oak fragments fell in between. Within oak, most birds fell into one of three groupings: 1) associated with conifer trees within oak fragments adjacent to coniferous forest, 2) associated with oak, an invasive alien shrub (Cytisus scoparius), and grass, within oak fragments adjacent to coniferous forest, and 3) associated with snowberry (Symphoricarpos albus) in oak fragments adjacent to urbanization. The results indicate that the type of adjacent habitat and tree composition in oak fragments are significant factors associated with oak bird assemblages. Future shifts in species composition are possible as the region becomes more urbanized and coniferous trees encroach into remaining oak habitat.